Soil chemical factors and grassland species density in Emas National Park (central Brazil)

Pk Amorim,Ma Batalha

doi:10.1590/s1519-69842008000200008

Abstract

Studies of grasslands on specific soil types suggest that different nutrients can limit biomass production and, hence, species composition and number. The Brazilian cerrado is the major savanna region in America and once covered about 2 million km(2), mainly in the Brazilian Central Plateau, under seasonal climate, with wet summer and dry winter. In view of the importance of soil chemical factors in the distribution of the vegetation forms within the Cerrado domain and which may influence the number of species, we analyzed some soil characteristics in three herbaceous vegetation forms -- hyperseasonal cerrado, seasonal cerrado, and wet grassland -- in Emas National Park, a core cerrado site, to investigate the relationship between number of species and soil characteristics. We collected vegetation and soil samples in these three vegetation forms and submitted the obtained data to multiple linear regression. We found out that aluminum and pH were the best predictors of species density, the former positively related to species density and the latter negatively related. Since the predictable variation in species density is important in determining areas of conservation, we can postulate that these two soil factors are indicators of high species density areas in tropical grasslands, which could be used in selecting priority sites for conservation.

Highlights

In herbaceous communities, the number of species and, biomass appear to present a humped-back relationship (Al-Mufti et al, 1977; Grime, 1979)
Aluminum and pH were the best predictors of species density, the former positively related to species density and the latter negatively related (Table 2)
Contrary to temperate grasslands (Janssens et al, 1998), the relationship between species density and major soil nutrients may be more complex in tropical grasslands, than in those grasslands within the Cerrado domain

Summary

Introduction

The number of species and, biomass appear to present a humped-back relationship (Al-Mufti et al, 1977; Grime, 1979). One may expect a humped-back relationship between the number of species and soil fertility as well (Janssens et al, 1998). In this case, species richness would be higher where nutrients are in short supply – and, plants do not grow tall and compete for light – and where environmental stress is not too excessive (Grime, 1979; Moore and Keddy, 1989).

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Conclusion